It’s not easy to make space habitable for humans. The International Space Station, which is only as long as a football field and not as roomy as two airplanes, is just 15 years old.

The human body can’t survive unprotected in space. That much we know. “If you don’t try to hold your breath, exposure to space for half a minute or so is unlikely to produce permanent injury,” explains NASA’s Imagine the Universe. “Various minor problems…start after 10 seconds or so. At some point you lose consciousness from lack of oxygen. Injuries accumulate.” Another minute or two, and you likely die.

But what about in a floating structure with the systems we need to breathe, the room we need to move and the food and water we need to live? In the 1970s, Princeton University physics professor Gerard O’Neill dreamed big, attempting to create a visual reality for what was then - and still is - a fantasy. The artist's renderings above give us a glimpse.

“New ideas are controversial when they challenge orthodoxy,” the late O’Neill wrote in Physics Today in 1974. “But I believe we have now reached the point where we can, if we so choose, build new habitats far more comfortable, productive and attractive” than Earth.

In 1975, O’Neill, in collaboration with NASA and the American Society for Engineering Education, asked 19 scientists, architects and students to answer the question, can humans permanently reside in space? For nearly three months, the group conceptualized how this theoretical floating spacecraft might function.

They came up with a wheel-like structure — picture a see-throw inner tube — about the size of a California beach town where 10,000 people “work, raise families and live out normal human lives,” according to a NASA write-up of the exercise. Despite being in space, it wasn’t devoid of weather, lit up by rays of the sun.

The sun really made the colony livable. It fostered excellent farming, what NASA called “agriculture of unusual productivity.” It generated electricity and energy to power solar furnaces, which allowed aluminum, titanium and silicon shipped into space to be refined. “With these materials,” NASA wrote, “they are able to manufacture satellite solar power stations and new colonies.” (Appropriately angled mirrors warded off cosmic radiation and helped the sun illuminate the colony.)

Is an orbiting interplanetary colony a reality today? NASA says that we know how to create one, but essentially, we haven’t figured out how to fund it. “How long did it take to build New York? California? France? Even given ample funds the first settlement will take decades to construct,” the agency reports. Give it at least 50 years.

For more about the 1975 space settlement project, click here. To enter the annual student space settlement contest put on by NASA and the National Space Society, click here.